In the tense and action-packed film set in 2009, Kane Kosugi stars as Joe Jinno, a former U.S. Navy SEAL who finds himself in a military jail cell in Roanoke, Virginia. His situation begins to change when Show Aikawa plays Detective Aguri Katsuragi, a dedicated Japanese detective who manages to secure Jinno's amnesty. Jinno’s refusal to eliminate innocent children during his missions previously led to his court-martial, highlighting his moral compass and refusal to kill those he perceives as innocent.
Later, Jinno is summoned by the U.S. Secretary of Defense to participate in a covert operation alongside Aguri. Their mission is to dismantle Blood Heat, a dangerous new drug circulating on the streets that acts as a super steroid, enhancing strength and aggression in users. The mastermind behind the drug's distribution is Lai Kenjin, played by Masaya Kato, who has established an underground fight ring known as the Muscle Dome. This brutal arena becomes the battleground where Kenjin’s top fighter, Lee Son-Min, portrayed by Ken Lo Wai-Kwong, uses Blood Heat to demolish opponents with ease, escalating the violence and chaos associated with this underground operation.
The story intensifies when Jinno and Aguri attempt to intercept a deal at a nightclub involving Kenjin and Russian drug dealers, but they are unsuccessful in stopping Kenjin's escape. During the chaos, Aguri is kidnapped and later found violently beaten and crucified in the Muscle Dome, a harrowing display of Kenjin’s cruelty. This incident reveals Kenjin's ruthless nature and his willingness to eliminate anyone who stands in his way, including his own half-brother Lai Kenkyo, whom Kenjin kills in a brutal manner after he refuses to help him with his criminal plans.
Following these events, Jinno tracks down Kenjin’s hideout and engages in a fierce fight against his henchmen. Despite his efforts, Jinno’s pursuit ends with Kenjin escaping by helicopter, while Jinno himself is arrested by a female cop named Misato Tachibana, who turns out to be Akane Katsuragi, Aguri’s sister. Demonstrating his resilience and fighting skills, Jinno manages to escape custody, knocking out Akane in the process.
As the story unfolds, Jinno’s path leads him to a cargo ship, where he narrowly evades capture. Along the way, he encounters and rescues a young girl named Haruka, whose father is revealed to be the creator of Blood Heat but was coerced into manufacturing the drug. Their journey takes them into the underground world of orphaned children, the so-called “rats,” led by the mysterious and unyielding Ken, played by Noboru Kaneko. These orphans are victims of Kenjin’s ruthless tactics, losing their parents either to Blood Heat’s destructive effects or to losses in underground fights.
Despite the initial reluctance of Ken and the other orphans to help, Ayane Katsuragi, played by Noriko Watanabe, joins Jinno and Haruka in their fight against Kenjin. The confrontation reaches its climax inside the Muscle Dome, where Jinno, fueled by the memory of Aguri’s death, unleashes his full strength against Lee Son-Min. Lee, under the influence of Blood Heat, fights brutally, but Jinno manages to defeat him after a fierce battle interrupted by Kenjin, who triggers explosions to destroy the arena.
Throughout the chaos, Ayane discovers that Ikkei Watanabe playing Detective Asakura was also complicit with Kenjin, leading to a confrontation where she is forced to shoot Asakura in self-defense. The final showdown takes place in an abandoned parking garage, where Jinno faces Kenjin in a brutal fight. They use sledgehammers, fighting fiercely until they two stand toe-to-toe with pure bare-handed combat. Just before the fatal blow, Jinno’s narration reveals his inner struggle and the drive behind his actions.
In the ultimate reveal, Jinno is shown walking out of the garage — a dark figure emerging from the shadows. Kenjin lies dead on the ground, and Jinno reunites with Ayane and the orphan children, celebrating the end of Blood Heat’s reign of terror. Ken, one of the orphaned “rats,” asks Jinno who he truly is, to which Jinno finally responds with a subtle, victorious smirk, marking a poignant conclusion to a story filled with violence, morality, and redemption.
